全文获取类型
收费全文 | 318篇 |
免费 | 14篇 |
国内免费 | 40篇 |
专业分类
化学 | 143篇 |
力学 | 4篇 |
数学 | 185篇 |
物理学 | 40篇 |
出版年
2023年 | 14篇 |
2022年 | 7篇 |
2021年 | 10篇 |
2020年 | 6篇 |
2019年 | 10篇 |
2018年 | 7篇 |
2017年 | 9篇 |
2015年 | 12篇 |
2014年 | 16篇 |
2013年 | 40篇 |
2012年 | 12篇 |
2011年 | 24篇 |
2010年 | 18篇 |
2009年 | 23篇 |
2008年 | 12篇 |
2007年 | 26篇 |
2006年 | 18篇 |
2005年 | 16篇 |
2004年 | 10篇 |
2003年 | 10篇 |
2002年 | 11篇 |
2001年 | 13篇 |
2000年 | 3篇 |
1999年 | 8篇 |
1998年 | 4篇 |
1997年 | 3篇 |
1996年 | 3篇 |
1995年 | 2篇 |
1994年 | 2篇 |
1993年 | 6篇 |
1992年 | 2篇 |
1991年 | 3篇 |
1990年 | 3篇 |
1989年 | 1篇 |
1988年 | 2篇 |
1987年 | 3篇 |
1984年 | 1篇 |
1982年 | 1篇 |
1978年 | 1篇 |
排序方式: 共有372条查询结果,搜索用时 18 毫秒
21.
交替惩罚三线性分解算法结合三维荧光光谱法同时分辨和测定酪氨酸、苯丙氨酸和色氨酸 总被引:1,自引:1,他引:0
用交替惩罚三线性分解算法(APTLD)结合三维荧光光谱法给出的二维数据对酪氨酸、苯丙氨酸和色氨酸进行了同时定性定量分析,为直接同时测定混合氨基酸中此三种物质提供了一种新的分析方法, 其测定相关系数分别为0.9987,0.9995和0.9993。采用超声波组织细胞破碎法对木槿叶中的氨基酸进行提取,利用APTLD法对提取液中氨基酸进行定量测定,测定相对标准偏差分别为0.84%,0.36%,1.59%, 回收率分别在101.0%~92.7%, 106.5%~93.0%, 103.0%~95.0%之间,方法简洁、快速、准确可靠,结果令人满意。 相似文献
22.
Bram Neirinck Lieve Van Mellaert Jan Fransaer Omer Van der Biest Jozef Ann Jef Vleugels 《Electrochemistry communications》2009,11(9):1842-1845
The possibility to use alternating current electrophoretic deposition (AC-EPD) to deposit living cells in the form of Staphylococcus aureus and Escherichia coli on stainless steel was assessed. The experimental results revealed that these bacteria can be successfully deposited on metallic surfaces from demineralized water and sucrose based solutions using asymmetric unbalanced electric fields. Cell viability of the deposited bacteria was influenced by the strain and deposition medium. 相似文献
23.
Mehmet Bac 《International Journal of Game Theory》2000,29(1):119-126
Strategic delay and restricted offers are two modes of signaling bargaining power in alternating offers bargaining games.
This paper shows that when both modes are available, the best signaling strategy of the “strong” type of the informed player
consists of a pure strategic delay followed by an offer on the whole pie. There is no signaling motivation for issue-by-issue
bargaining when the issues are perfectly substitutable.
Received: July 1996/Final version: August 1999 相似文献
24.
The cyclic projections algorithm is an important method for determining a point in the intersection of a finite number of closed convex sets in a Hilbert space. That is, for determining a solution to the “convex feasibility” problem. This is the third paper in a series on a study of the rate of convergence for the cyclic projections algorithm. In the first of these papers, we showed that the rate could be described in terms of the “angles” between the convex sets involved. In the second, we showed that these angles often had a more tractable formulation in terms of the “norm” of the product of the (nonlinear) metric projections onto related convex sets.In this paper, we show that the rate of convergence of the cyclic projections algorithm is also intimately related to the “linear regularity property” of Bauschke and Borwein, the “normal property” of Jameson (as well as Bakan, Deutsch, and Li’s generalization of Jameson’s normal property), the “strong conical hull intersection property” of Deutsch, Li, and Ward, and the rate of convergence of iterated parallel projections. Such properties have already been shown to be important in various other contexts as well. 相似文献
25.
We study combinatorial properties of the alternating subgroup of a Coxeter group, using a presentation of it due to Bourbaki. 相似文献
26.
Aaron J. Molstad Adam J. Rothman 《Journal of computational and graphical statistics》2019,28(1):11-22
We propose a penalized likelihood method to fit the linear discriminant analysis model when the predictor is matrix valued. We simultaneously estimate the means and the precision matrix, which we assume has a Kronecker product decomposition. Our penalties encourage pairs of response category mean matrix estimators to have equal entries and also encourage zeros in the precision matrix estimator. To compute our estimators, we use a blockwise coordinate descent algorithm. To update the optimization variables corresponding to response category mean matrices, we use an alternating minimization algorithm that takes advantage of the Kronecker structure of the precision matrix. We show that our method can outperform relevant competitors in classification, even when our modeling assumptions are violated. We analyze three real datasets to demonstrate our method’s applicability. Supplementary materials, including an R package implementing our method, are available online. 相似文献
27.
We extend Stanley's work on alternating permutations with extremal number of fixed points in two directions: first, alternating permutations are replaced by permutations with a prescribed descent set; second, instead of simply counting permutations we study their generating polynomials by number of excedances. Several techniques are used: Désarménien's desarrangement combinatorics, Gessel's hook-factorization and the analytical properties of two new permutation statistics “DEZ” and “lec.” Explicit formulas for the maximal case are derived by using symmetric function tools. 相似文献
28.
Let G be a finite alternating or symmetric group. We describe an infinite class of finite lattices, none of which is isomorphic to any interval [H,G] in the subgroup lattice of G. 相似文献
29.
Elena Kireeva 《代数通讯》2019,47(2):490-501
The double centralizing theorem between the action of the symmetric group Sn and the action of the general linear group on the tensor space Tn(W) was obtained by Schur. Here we obtain a double centralizing theorem when Sn is replaced by the wreath product of a finite group G and the alternating group An. 相似文献
30.
Here we report the characterization of an electrochemical mercury (Hg2+) sensor constructed with a methylene blue (MB)-modified and thymine-containing linear DNA probe. Similar to the linear probe electrochemical DNA sensor, the resultant sensor behaved as a “signal-off” sensor in alternating current voltammetry and cyclic voltammetry. However, depending on the applied frequency or pulse width, the sensor can behave as either a “signal-off” or “signal-on” sensor in square wave voltammetry (SWV) and differential pulse voltammetry (DPV). In SWV, the sensor showed “signal-on” behavior at low frequencies and “signal-off” behavior at high frequencies. In DPV, the sensor showed “signal-off” behavior at short pulse widths and “signal-on” behavior at long pulse widths. Independent of the sensor interrogation technique, the limit of detection was found to be 10 nM, with a linear dynamic range between 10 nM and 500 nM. In addition, the sensor responded to Hg2+ rather rapidly; majority of the signal change occurred in <20 min. Overall, the sensor retains all the characteristics of this class of sensors; it is reagentless, reusable, sensitive, specific and selective. This study also highlights the feasibility of using a MB-modified probe for real-time sensing of Hg2+, which has not been previously reported. More importantly, the observed “switching” behavior in SWV and DPV is potentially generalizable and should be applicable to most sensors in this class of dynamics-based electrochemical biosensors. 相似文献